The class of linear alternating polymers of carbon monoxide and at least one olefinically unsaturated hydrocarbon has been known for some time. Such polymers were produced by Nozaki, e.g., U.S. Pat. No. 3,694,412, using arylphosphine complexes of palladium moieties as catalysts and certain inert solvents. More recent methods for the production of such linear alternating polymers, now known as polyketone polymers or polyketones are illustrated by a number of published European Patent Applications including nos. 121,965, 181,014, 213,671, and 257,663. The processes generally involve the use of a catalyst composition formed from:
a) a compound of a Group VIII metal
b) an anion of a strong non-hydrohalogenic acid, and
c) a phosphorus bidentate ligand of the general formula (R)(R)P--R'--P(R)(R) in which R independently is a hydrocarbyl or substituted hydrocarbyl group, and R' represents a divalent organic bridging group which contains from two to four carbon atoms in the bridge connecting the two phosphorus atoms.
Preferred catalyst compositions are formed from:
a) a compound of a Group VIII metal selected from palladium, cobalt or nickel,
b) an anion of a non-hydrohalogenic acid with a Pk.sub.a of less than 2,
c) a phosphorus bidentate ligand of the general formula (R)(R)P--R'--P--(R)(R) in which R and R' have the previously indicated meaning.
It has now been found that the polymerization activity of these catalyst compositions can be greatly improved by incorporating therein a weak acid.